316 installation, a Portland cement based thinset mortar for setting of floor and wall tiles for interior applications. Due to its self-drying Portland cement formulation, MarbleFlex will not contribute moisture to marble or stone tile, making it suited for use with moisture-sensitive tile and stone. The quick drying formula allows tile and stone to be grouted in only 2 hours. For use with marble (including black and green marble), granite, stone tile, ceramic tile, mosaics, and pavers. For porcelain and nonabsorbent tiles use Henry 348 CeMastic Universal Tile Setting Adhesive (refer to Model No. FP00348407). MarbleFlex bonds to concrete, concrete backer board units, masonry, cement terrazzo, drywall, and other common building surfaces on interior floors, walls, and countertops. Easy-to-mix, just add water. 12.5 lb. will cover 19 to 22 sq. ft. when using a 1/4" x 1/4" x 1/4" square notched trowel, or 16 to 19 sq. ft. using a 1/4" x 3/8" x 1/4" square notched trowel. Do not expose to freezing. Use clean, damp cloth for clean up. If material dries, use mechanical means to remove. 12.5 lb. box.